Needle-shaped 3C-SiC nanowires were grown from commercially available SiC powders in a thermal evaporation process with iron as catalyst. A strong broad photoluminescence peak located around 450 nm was observed at room temperature, which may be ascribed to quantum size effects of nanomaterials. Needle-shaped 3C-SiC nanowires may have great potential applications such as blue-green light-emitting diodes and display devices.

The one- and the two-photon absorption rates of conduction-band electrons (CBEs) in dielectric materials are calculated by second-and third-order perturbation theory, respectively. Here fused silica irradiated under 526 nm ultra-short pulse laser is used as an example. Compared with the case that only the one-photon absorption of CBE assisted by a phonon is considered. the rate of total energy gain of CBE from laser field will be enhanced by a factor of 3 when both of the one-and the two-photon absorption are included. The avalanche rate includes not only the term proportional to laser intensity, but also the terms proportional to the square of laser intensity and to the product of laser intensity and hole density. The damage threshold is calculated on the basis of the avalanche model, and find it is lowered by about 15% compared with the case for only the one-photon absorption of CBE assisted by a phonon is considered. The theoretical value agrees well with experimental results.

We report the single-shot damage thresholds of MgF2/ZnS omnidirectional reflector for laser pulse durations from 50 fs to 900 fs. A coupled dynamic model is applied to study the damage mechanisms, in which we consider not only the electronic excitation of the material, but also the influence of this excitation-induced changes in the complex refractive index of material on the laser pulse itself. The results indicate that this feedback effect plays a very important role during the damage of material. Based on this model, we calculate the threshold fluences and the time-resolved excitation process of the multiplayer. The theoretical calculations agree well with our experimental results.

The rate at which conduction-band electrons (CBE) absorb laser energy is calculated by both the quantum mechanical and the classical methods. Here fused silica irradiated with a 780-nm femtosecond-pulse laser is used as an example. It is found that the rate obtained by the quantum mechanical method is about one-third of that by the classical method, and it is much less than the direct-current limit. In the flux-doubling model, the avalanche rate in fused silica is 4I ps−1 obtained by the quantum mechanical method, while it is about 13.7 I ps−1 by the classical method, where the laser intensity I is in units of TWcm−2. The differential equation of the evolution of CBE density is solved numerically, and it is found that the combination of CBE–hole recombination, CBE diffusion and initial CBE density (<1013 cm−3) is not important. The dependence of avalanche breakdown threshold on laser-pulse duration is presented. The threshold calculated by the quantum mechanical method agrees well with experimental results, while the threshold obtained by the classical method differs greatly from the experiments.

Two collinear femtosecond laser pulses, one at wavelength of 800nm and the other at 400nm (double frequency), simultaneously irradiated the surface of ZnSe crystal, which resulted in regular nanograting with period of 180 nm on the whole ablation area. We attribute the formation of the nanograting to be due to the interference between the surface scattered wave of 800 nm lasers and the 400nm light. The period of the nanograting is aboutλ/2n, where n is refractive index of the sample, andλ, the laser wavelength. This mechanism is supported by observation of rotation of the nanograting with the polarization of 400nm light, and by the dependence of λ of the nanoripples on the surface of semiconductors and dielectrics.